FIG. 1a illustrates a fluorescent lamp's electronic ballast 100. The electronic ballast 100 includes a half-bridge circuit 105, a drive circuit 110, and a load circuit 115. The half-bridge circuit 105 may include two semiconductor switching elements, Q1 120 and Q2 122, which are connected in series with respect to voltage supply terminals T1 and T2 of a voltage supply that supplies a direct current (DC) voltage with potential Vb. The drive circuit 110 generates two control signals, S1 and S2, that may be used to control the state of the two semiconductor switching elements. FIG. 1b illustrates a semiconductor switching element, such as the semiconductor switching element Q1 120. The semiconductor switching element Q1 120 may use a wide variety of semiconductor transistors, such as an N-type enhancement mode MOSFET. However, other types of semiconductor transistors may be used as the semiconductor switching element Q1 120, including N- and P-type JFETs, N- and P-type depletion mode MOSFETs, P-type enhancement mode MOSFETs, and so forth.
The drive circuit 110 may be configured so that the two control signals are generated in such a manner that the two semiconductor switching elements are never switched on simultaneously. A time when both semiconductor switching elements are switched off may be referred to as a dead time. During the dead time, a voltage potential across the load circuit 115 may be brought up (or down) to being substantially equal to either the voltage potential of the voltage supply Vb (or ground). With both terminals of a semiconductor switching element at the same or substantially the same potential, the drive circuit 110 may then generate an appropriate control signal to switch the state of semiconductor switching element. The switching with both terminals of the semiconductor switching element at the same or substantially the same voltage potential is commonly referred to as zero voltage switching (ZVS). ZVS offers high efficiency since there is no or very little power dissipated in the semiconductor switching element while switching. However, if the dead time's duration is too long (or too short), then the ZVS condition may no longer exist (or may have not yet occurred).